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Plate freakin' tectonics!

I'm reading the second edition of "the science of the discworld", and learning all kinds of neat things.

Did you know that the evidence for plate tectonics is not just preserved by the coastlines of the continents, but my their interiors? Consider the magntic field of the Earth. Whenever new rocks solidify from the volcanic eruptions, they pick up a readable trace of that magnetic field. Every half a million years or so, the polarity of the Earth's magnetic field reverses, relatively suddenly. Guess what you find if you measure the fields embedded in the rocks all across a continent?

A consistent pattern of stripes! Stripes which follow the movement of the plates, and match in thickness with their companion stripes on previously connected land masses!!